Adjustable blackboard t-square



M. L. CURTS. ADJUSTABLE BLACKBOARD T-SQUARE.

APPLICATION FILED JUNE 23,1920. l

Patented Dec. 13, 1921.

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ADJUSTABLE BLACKBOABD T-SQUARE.

APPLICATION FILED JUNE 23. 1920.

Patented Dec. 13, 1921.

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MILO L. CURTS, 0F BLOOMINGTON, INDIANA.

ADJUSTABLE BLACKBOARD T-SQUARE.

Specification of Letters Patent. Patented Dec.,13, 1921.

Application filed. June 23, 1920. Serial No. 391,027

To all whom it may concern:

Be it known that I, MILO LEE; CUn'rs, a citizen of the United States, and a resident of Bloomington, in the county of Monroe and State of Indiana, have invented certain new and useful'lmprovements in Adjustable Blackboard T-Squares, of which the following is a specification.

This invention relates to the class of measuring, and more particularly'to geometrical measuring instruments, the object of theinvention being to provide an improved T-square having an adjustable supporting arm constructed in a simple and novel manner for mounting the same upona blackboard and provided with a blade, whereby drawings may be executed with facility, and

. particularly for instruction purposes, the

, durability, the parts being so related and- T-square being adapted for use in cooperation with triangles, as in the ordinary use of a T-square. I

-More especially, the invention comprehends the provision of an adjustable blackboard T-square, which consists of a supporting arm constructed and arranged in a novel manner for lengthwise adjustment so as'to permit the convenient engagement and disengagement thereof with the ledges or upper and lowering moldings at the edges of the blackboard with the blade extending across the board and adjustable'along the arm to facilitate the execution of the drawings, while the arm is provided with improved means for'supporting the device in position.

A further object of the invention is to construct the T-square with a view to simplicityof construction and use, as well as connected as to insure accuracy of measurement at all times. 7

Other and further objects of my invention 'will become readily apparent to persons skilled in the art, from a consideration of the following description when taken in conunction with the accompanying drawings,

- wherein Figure l is a front elevation showingmy improved adjustable blackboard T-square appliedto a blackboard as when in use,

Fig. 2 is an enlarged face view of the T-square detached,

Fig. 3 is a side elevation thereof as shown in Fig. 2, the blade being shown in section,

Fig. 4 is a transverse sectional view taken on the line 4.-4c of Fig. 2,

Fig. 5 is a similar view taken on the line 55of Fig. 2 and looking in the direction indicated by the arrows, and

Fig. 6 is a transverse sectional view taken onthe line 6-.6 of Fig. 3.

Referring to the drawings in detail, in which like reference characters designate corresponding parts throughout the several views, the T-square is shown as comprising a supporting arm 10 consisting of a bottom section 11 and a top section 12, both being relatively. flat and-preferably formed .of wood. The bottom section 11 is provided with a longitudinal groove in its topface, as indicated at 13, and the top section 12 is provided with rabbeted sideedges 1 1 produoing an intermediate longitudinal projection'or tongue 15 fitting the groove 13 for free sliding movement therein. The top section 12 extends-beyond the ends ofthe central longitudinal slot16 terminating at a spaced distance from the lower end, while opposite or upper end. 1 [Secured to the bottom section and extendextendin to and communicating with the,

' ing at right angles therefrom and from the top section,is a blade 17,.the same being preferably secured or fastened tothe bottom section or intermediate sliding head ofthe supporting arm .orhea'd proper of the VT square as by means of four fiat head screws 18, so that the blade is accurately and securely fastened in position and its weight supported in a true horizontal position. I I'IOWGVGLdI-h blade may be [adjusted vertically along the arm,; longitudinally with respect to the latter, through themedium of a clamping device consisting ofapbolt 19 having anenlarged head 20 embedded in a recess 21 in the bottom section or intermediate sliding head vI1 and extending therethrough, and through the slot 16, the threaded. projectingend of the bolt having a suitable binding or wing nut 22 engaged.

thereon for frictional contact :with the front face of the arm, in order to hold the blade in any desired and adjusted position longitudinally of the supporting arm.

At the lower end of the supporting arm,

there is provided a stationary head or block 23which is grooved in a manner correspond ing to the formation of the intermediate head or bottom portion 11 for secure attachment'to the supporting arm and in perfect alinement therewith at theside edges of said parts.

At the opposite or upper end of the supporting arm, there is arranged an adjustable head or block 24 grooved to lit the projection or tongue of the supporting arm formed by the top section 12 and movable freely along the same, in order that the length of the supporting arm may be adjusted so that the device may be securely held or clamped between the ledges or moldings of a blackboard or the like. In order that the head 24 may be properly adjusted and held in clamping relation to the supporting arm proper, a bolt 25 similar to the bolt 19 is engaged through a central aperture therethrough, the head of the bolt being likewise embedded and a binding nut 26 being engaged on the exposed threaded end thereof, in order to hold the head against movement by frictional engagement with the face of the arm.

Thus, it will be seen that while the block or head 23 is securely fastened to the arm as through the medium of screws 27 extending up from the bottom face at the tongue and groove area, and by means of the screws 28 extending through thesides and engaging the tongue 15 and the side projections 29 of the head outwardly of the groove therein,

' the block or head 24 at the upper end may be adjusted longitudinally of the arm, inwardly of, in alinement with or'to project from said end, sufiicient adjustment being of the device may be secured. Each head is provided with a gripping means consisting of a toothed plate 29 of right angular formation, said plate being preferably of metal such as steel and embedded in the bottom and end faces thereofwith the teeth 30 projecting from the ends in two rows so that said blocks or heads are held flat against the parts engaged by the toothed steel grips. These plates are preferably secured in position by means of screws 31 extending upwardly through the blocks and into the side projections thereof independently of the arm. In addition, the faces of the blocks or heads 23 and 24 and the intermediate head or bottom portion 11 are suitably covered with felt or the like, as indicated at 32, in order to prevent injury to the writing surface of the blackboard.

In Fig. l of the drawings, I have shown the device applied to a blackboard 33 having the top and bottom ledges or moldings 34 which project from the plane of the blackboard writing surface and between which the arm is arranged in a vertical position. In applying the device, the teeth of the head 23 at the lower end of the supporting arm are engaged with or caused to penetrate the wood molding at the bottom of the board anduthe clamping means of the head like.

24 loosened, in order that the teeth thereof may be forced into the upper molding or ledge, when the clamping member or nut 26 is tightened on the bolt 25, thus securely retaining the arm in position. The blade 17 may be adjusted along the supporting arm. through the medium of the intermediate slidable 'head or bottom section 11, the felt or cloth cushioning surface of the latter moving along the face of the board without injury thereto. As the bottom section 11 is held in true alinement with the supporting arm or top section 14, and as the blade is rigidly secured to the bottom section or head 11 so as to extend at right angles therefrom, the blade will be supported in a true horizontal position and maybe adjusted vertically to different horizontal planes and to extend substantially across the board, as is particularly indicated in Fig. 1 of the drawings. v

The device is of especial advantage in connection with shop work where a board mounted upon a support or easel 35, is pro vided and drawings may be very conveniently and accurately executed, employing triangles in cooperation with the support ing armand blade, as in ordinary drafting work. Furthermore, in view Of the foregoing, it is thought that the operation of the device will bereadily understood and in view of the simplicity and practical value, that it will commend itself to those skilled j in the art. allowed, in order that proper attachment It will also appear that the adjustable head is adapted to move in a plane parallel to or in alinement with the axis of the supporting arm, thus maintaining the true rectilinear formation of the arm and insuring that it will be disposed in aproper or true vertical position between the ledges or mold ings of the blackboard, with the blade extending in a horizontal position at right angles therefrom, across the face of the board.

Having thus described my invention, what I claim is 1. An adjustable blackboard T-square comprising a supporting arm capable of lengthwise adjustment and a blade carried by the arm, said arms having gripping means at the ends thereof adapted to engage and bite into the inner faces of the top and bottom ledges of a blackboard frame or the 2. An adjustable blackboard T-square adapted for use with blackboards having opposed top and bottom ledges comprising an adjustable supporting arm having means 7 for positively engaging said ledges at the inside thereof tosecure the arm in position, and a blade supported by the arm to extend across the board. I 3. An adjustable blackboard T-square adapted for use with. blackboards having op posed ledges comprising an adjustable supporting arm having spaced rows of teeth for engaging said ledges at the inside to secure the arm in position, and a blade extending at right angles to the supporting arm and adjustable along the same. I

4:. An adjustable blackboard T-square adapted for use with blackboards having opposed ledges comprising an adjustable supporting arm having means for engaging said ledges to secure the arm in position, said supporting arm being provided with releasable clamping means'on at least one of the ends thereof and a supporting and drawing instrumentality extending from and supported by the arm. y

5. For use 'in connection with a blackboard having top and bottom moldings projecting from the writing surface thereof, a drawing device comprising an arm having means at the end thereof to penetrate said moldings and frictionally hold the arm in position, said arm'being extensible in a line uniform with the axis thereof.

6. For use in connection with a blackboard having top and bottom moldings projecting from the writing surface thereof, a drawing device comprising an arm having means at the end thereof to penetrate said moldings and frictionally hold the arm in position', said arm being extensible in aline uniform with the axis thereof, and a drawing instrumentality carried by the arm and adjustable vertically along the same, said instrumentality being adapted to be held in a fixed position and arranged to extend across the surface of the board.

7. For use in connection with a blackboard having top and bottom moldings projecting from the writing surface thereof, a T-square. comprising a supporting arm, heads at the ends of said arm and provided with means to engage said moldings, said arm being extensible, and means to hold the arm in adjusted extensible position rectithe arm may be removed.

8. For use in connection with blackboards having top and bottom moldings projecting from the writing surface thereof, a T-square comprising a longitudinally slotted arm adapted to be arranged vertically between said moldings, heads at the ends of said arm and in alinement therewith, said arm being of rectilinear formation, engaging means carried by said head to grip said moldings, means for adjusting at least one of said heads longitudinally in said slot and to hold the same in adjusted clamped or released position, and a blade carried by the arm and having clamping means adjustable in the slot thereof.

9. For use in connectionswith a blackboard having top and bottom moldings projecting from the writing surface thereof,

a T-square comprising a longitudinally slotted arm adapted "to be arranged vertically between said moldings, heads at the ends of said arm and in alinement therewith, said arm being of rectilinear formation, engaging means carried by said head to grip said moldings, means for adjusting at least one of said heads longitudinally in said slot and to'hold the same in adjusted, clamped or released position, protective coverings for said heads to engage the surface of the board, an intermediate head carried by the arm, connecting means between the intermediate head and arm to hold the head in adjusted position in alinement with the axis thereof between the first named heads and a blade rigidly carried by and projecting from the intermediate head.

l0. A T-square of the' class described, comprising a supportingarm comprising a top section and a bottom section forming a head, said bottom section being positioned intermediately of the top section andhaving interfitting engagement therewith, clamping means between said sections, and. a blade rigidly fixed to the bottom section and extending at right angles with respect to said sections.

11. A T-square of the class described, comprising a supporting arm comprising a top section and a bottom section forming a head, said bottom section being positioned intermediately of the top section and having interfitting engagement therewith, clamping means between said sections, a blade rigidly fixed to the bottom section and extending at right angles'with respect to said sections, and projecting means at the ends of the top section of the arm having means to frictionally and bindingly engage the ledges of a blackboard or the like.

12. An adjustable blackboard T-square comprisinga supporting arm consisting of a rectilinear top section having a projecting tongue and rabbeted side edges, said section being formed with a longitudinal slot communicating withone end, a bottom section forming an intermediate head and having a groove receiving said tongue and side projections fitting said rabbeted edges for adjustment of said bottom section with respect to the top section lengthwise and with tom section, and a blade carried by said bottom section, saidtop and bottom sections having cooperative means to hold the latter in adjusted position. 13. An adjustable blackboard T-squar comprising a supporting arm consisting of a rectilinear top sectionhaving a projecting tongue and rabbeted side edges, said section being formed with a longitudinal slotcomforming an intermediate head and having a groove receiving said tongue and side projections fitting said rabbeted edges for adjustment of said bottom section with respect to the top section lengthwise and with the edges in alinement, engaging heads at the ends of the top sections, a blade seated in the bottom face of said bottom section and rigidly secured thereto, clamping means engaged through said sections at the slot of the top section to hold the bottom section in adjusted position longitudinally of the supporting arm, a fixed head block at one end of the arm and carried by the top section thereof, an adjustable head section at the other end of the arm, and also carried by said top section, and clamping means between the last named head and top section whereby the arm is rendered extensible in length and adapted to be shortened in applying and removing the same.

14. An adjustable blackboard T-square comprising a supporting arm consisting of a rectilinear top section having a projecting tongue and rabbeted side edges, said section being formed with a longitudinal slot communicating with one end, a bottom section forming an intermediate head and having a groove receiving said tongue and side projections fitting said rabbeted edges for adjustment of said bottom section with respect to the top section lengthwise and with the edges in alinement, engaging heads at the ends of the top sections, a blade seated in the bottom face of. said bottom section and rigidly secured thereto, clamping means engaged through said section at the slot of the top section to hold the bottom section in adjusted position longitudinally of the supporting. arm, a fixed head block at one end of the arm and carried by the top section thereof, an adjustable head section at the other end of the arm and also carried by said top section, toothed plates carried by said heads with the teeth thereof projecting from the ends, and felt coverings for said intermediate bottom section and heads.

MILO 'L. CURTS. 

